Switching methods for a single result.

Question

Heyall,

I have a situation where I require to consult different objects in PHP via different methods to find some data.

The question regards more about formatting the code than an actual programming issue. What I am trying to do is not using several if's to gather this data like:

$data = obj->getData();
if (!isset($data)) $data = othObj->getThisData();
if (!isset($data)) $data = anothObj->getTheData();
if (!isset($data)) $data = anothOne->getAData();
...
process($data)

I was wondering what are the best practices in this case, if there is a better way using another procedures, like foreach or switch/case.

Thanks!

Answer 1

1. It doesn't look too bad the way it is.

2. It could be a bit more efficient if the if's were nested. e.g.

    if (!isset($data = othObj->getData()))
    if (!isset($data = othObj->getThisData()))
    if (!isset($data = anothObj->getTheData()))
    $data = anothOne->getAData()))
    // ...
    process($data)
   

   Since there are less calls to isset (though they're pretty cheap anyway, so I wouldn't worry about it).

Answer 2

Personally I'd do something like this:

$data = null;

if (isset($obj->getData()) $data = $obj->getData();
else if (isset($othObj->getThisData()) $data = $othObj->getThisData();
else if (isset($anothObj->getTheData()) $data = $anothObj->getTheData();
else if (isset($anothOne->getAData()) $data = $anothOne->getAData();

process($data)

This saves processing time if the earlier objects actually return something. Since it is an elseif setup once it finds data it'll stop processing the other if clauses.

I don't think a switch statement would be appropriate in this case. Switches tend to be testing the value of one variable (is $a = 1, 2, 3 or 4).

Answer 3

You can make an array of the possible objects you want to try, then run a loop. Might be more maintainable. This code can be modified to include parameters and use call_user_func_array instead.

$dataCallback = array(
    array($othObj, 'getData'),
    array($othObj, 'getThisData'),
    array($anothObj, 'getTheData'),
    array($anothOne, 'getAData'),
);

for($i = 0, $t = count($dataCallback); !isset($data) && $i < $t; $i++) {
  $callback = $dataCallback[$i];
  $data = call_user_func($callback);
}

if (isset($data))
  process($data);
else
  //no valid data returned at all ...

Answer 4

($data = $ob1->get()) || ($data = $ob2->get()) || ($data = $ob3->get());

Would work, but if you're get function returns an empty array or false or empty string instead of NULL, it's going to continue looking for data...

Answer 5

I'd probably group the objects to ask for data into an array:

$objArray = array($obj, $othObj, $anothObj, ... );

Then run through a while loop until I had data:

$i = 0;
do {
   $data = $objArray[$i]->getData();
   $i++;
} while(!isset($data) && $i < count($objArray));